Conventional burners as for example known from the DE10128063 may be equipped with a lance for introducing gaseous and/or liquid fuels into the burner. The introduction of fuel via the lance may be utilized, for example, for pilot operation or for stabilizing a combustion reaction in the combustion space of a combustion chamber. Usually, a shaft of such a lance has at least one nozzle for introducing fuel into the burner. An example for such a fuel lance is given in the DE4326802.
Conventional burners preferably operate with natural gas as gaseous fuel. In this case, it is customary to provide the lance shaft along its circumference with a plurality of nozzles, through which the fuel gas can flow out essentially radially with respect to a longitudinal mid-axis of the shaft. A main injection direction of the respective nozzle is thereby oriented essentially radially onto a burner wall. In conjunction with an oxidizer gas flow present in the burner during operation, the fuel gas emerging radially from the lance is entrained in the main flow direction of the oxidizer gas, thus resulting in the desired intermixing between the oxidizer gas and fuel gas.
In modern combustion chambers, other gaseous fuels may also be used, which are distinguished by increased reactivity, as compared with a natural gas. These are, for example, fuel gases which contain hydrogen gas and, moreover, may contain carbon monoxide gas. Such a fuel gas containing hydrogen gas and carbon monoxide gas can be generated, for example, by means of the partial oxidation of long-chain hydrocarbons. A fuel gas of this type may also be designated as synthesis gas or syngas. If, then, a synthesis gas of this type is used as fuel gas in a conventional burner, this may lead to difficulties, since conventional burners are not suitable per se for use with fuel gases having such high reactivity. For example, reactive fuel gases of this type ignite even at lower temperatures and therefore with markedly shorter dwell times in the burner. In order in this case to avoid a hazardous flashback, for example, the mass flow of fuel gas can be increased correspondingly. Further, these gases have a lower calorific value than natural gas. Thus, higher mass and volume flows are needed, resulting in changed fuel distribution when fuel is injected from conventional natural gas holes. With an increased fuel mass flow, however, an undesirable enrichment of fuel gas in the region of the burner wall may occur, with the result that an intensive intermixing with the oxidizer gas, which is preferably air, takes place only inadequately. Inadequate intermixing, however, may lead to increased combustion temperatures, thus ultimately entailing increased pollutant values. Further, if fuel is concentrated near the wall, a flame can stabilize in the wall region due to low flow velocities in the wall, which can quickly lead to severe damages on the hardware.